Daniel Smith
Posts: 970
Joined: Sep. 2007
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| Quote (Albatrossity2 @ Mar. 08 2009,10:38) | | Quote (Daniel Smith @ Mar. 08 2009,12:00) | | Macrophomate synthase is a multitasking enzyme for sure (Thanks for that). |
Daniel seems to have sauntered off without addressing the multi-tasking enzymes I pointed him toward in my earlier comment.
Imagine that. Do you suppose that there is something in one of those examples that did not fit with his presuppositional conclusion?
| Quote | Elimination of competing hydrolysis and coupling side reactions of a cyclodextrin glucanotransferase by directed evolution.
Ronan M. KELLY*†, Hans LEEMHUIS*†, Henriëtte J. ROZEBOOM‡, Niels van OOSTERWIJK‡, Bauke W. DIJKSTRA‡ and Lubbert DIJKHUIZEN*†1
*Microbial Physiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, †Centre for Carbohydrate Bioprocessing, TNO-University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands, and ‡Laboratory of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
Thermoanaerobacterium thermosulfurigenes cyclodextrin glucanotransferase primarily catalyses the formation of cyclic ?-(1,4)-linked oligosaccharides (cyclodextrins) from starch. This enzyme also possesses unusually high hydrolytic activity as a side reaction, thought to be due to partial retention of ancestral enzyme function. This side reaction is undesirable, since it produces short saccharides that are responsible for the breakdown of the cyclodextrins formed, thus limiting the yield of cyclodextrins produced. To reduce the competing hydrolysis reaction, while maintaining the cyclization activity, we applied directed evolution, introducing random mutations throughout the cgt gene by error-prone PCR. Mutations in two residues, Ser-77 and Trp-239, on the outer region of the active site, lowered the hydrolytic activity up to 15-fold with retention of cyclization activity. In contrast, mutations within the active site could not lower hydrolytic rates, indicating an evolutionary optimized role for cyclodextrin formation by residues within this region. The crystal structure of the most effective mutant, S77P, showed no alterations to the peptide backbone. However, subtle conformational changes to the side chains of active-site residues had occurred, which may explain the increased cyclization/hydrolysis ratio. This indicates that secondary effects of mutations located on the outer regions of the catalytic site are required to lower the rates of competing side reactions, while maintaining the primary catalytic function. Subsequent functional analysis of various glucanotransferases from the superfamily of glycoside hydrolases also suggests a gradual evolutionary progression of these enzymes from a common ‘intermediate-like’ ancestor towards specific transglycosylation activity. |
Hmm. A naturally occurring (presumably intelligently designed) enzyme has an undesirable side-reaction, probably derived from an ancestral enzyme. Human designers are able to reduce the level of this side-reaction by modifying (randomly!) the protein sequence, thus improving on the enzyme that Daniel's God generated. Oh, the horror! |
I did read that Albatrossity. I also read the other article you linked to.
I must remind you that I've never stated that God's designs were immutable. In fact I've stated on more than one occasion that they were designed to evolve.
In the case you quote from, I can only assume that the "undesirable" side reaction produces no ill effects for the organism and that the part of the enzyme that is "optimized" is the important part. I'll also remind you that "thought to be" and "suggests" are not terms used in response to overwhelming evidence but rather to clues that may or may not lead to such a conclusion when more evidence is found.
Do they mix their mutated bacteria with the originals in a natural setting to see how well they compete?
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"If we all worked on the assumption that what is accepted as true is really true, there would be little hope of advance." Orville Wright
"The presence or absence of a creative super-intelligence is unequivocally a scientific question." Richard Dawkins
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